Curse the gts 450, it has only 128 bit bus . And my actual 9600 gt has 256 .

It honestly doesn't make sense to even look at the memory bandwidth of the card in your situation. At that low of a resolution, core/shader clocks are a much bigger factor. In fact performance between the 3 different GTX 460's would theoretically be identical for you. Now of course if you plan on a significant monitor upgrade that would be a different story. But since you're aiming fairly low on the GPU selection, I would assume you wouldn't be aiming higher than 1680x1050 on the monitor end. (which is still a low enough resolution for low memory bandwidth cards)